Hitherto, for the purposes of improving fuel efficiency and reducing an environmental load of automobiles, and for other such purposes, there have been developed automatic idle-stop systems for automatically performing an idle stop with the satisfaction of a predetermined condition. However, it takes time for the engine rotation to be completely stopped by a friction force, and a conventional idle-stop system cannot carry out the restart during this period.
Thus, as a method for solving this problem, for example, there is a method involving, in a start control device for an internal combustion engine, when start rpm determination means determines that the rpm of the internal combustion engine decreases to an rpm enabling engagement of a rotation drive mechanism with the internal combustion engine, engaging the rotation drive mechanism with the internal combustion engine, thereby rotationally driving the internal combustion engine (for example, refer to PTL 1).
Moreover, there is an engine automatic stop/start control device including a starter capable of individually actuating a motor for rotationally driving a pinion, and an actuator for causing the pinion to mesh with a ring gear coupled to a crankshaft of an engine. If, in an engine rotation decreasing period in which the engine rpm decreases due to an automatic stop of the engine, an engine restart request is generated when the engine rpm is in a predetermined rpm area, after or while the engine automatic stop/start control device causes or is causing the pinion to mesh with the ring gear by the actuator, the engine automatic stop/start control device rotates the pinion by the motor, thereby starting cranking by the starter, and restarts the engine (for example, refer to PTL 2).
Moreover, there is known an engine starting device for carrying out determination processing of determining, when a restart request for an engine occurs, whether or not an engine rpm is equal to or lower than a predetermined meshing enabling rpm, first electric power supply processing of supplying a solenoid with electric power when the determination processing determines that the engine rpm is equal to or lower than the meshing enabling rpm, condition determination processing of determining whether or not a predetermined condition is established after the first electric power supply processing, and second electric power supply processing of supplying the starter motor with electric power when the condition determination processing determines that the condition is established (for example, refer to PTL 3).